In many roofing applications, for example in large, flat commercial roof decks, a roofing membrane is used to seal and protect the roof deck from environmental weather conditions. The roofing membrane may be made of various materials, such as polymeric materials including EPDM (ethylene propylene diene M-rubber) or TPO (thermoplastic polyolefin). The roofing membrane is adhered overtop insulation boards or panels. The insulation boards are typically secured to the roofing substrate or roof deck via an adhesive composition. A conventional adhesive composition used to adhere the insulation boards to the roof deck includes polyurethane. The polyurethane adhesives are oftentimes applied directly onto the roof deck via an applicator system and the insulation boards are then laid onto the roof deck surface. Conventional polyurethane adhesives oftentimes include two separate parts that are mixed by an applicator just prior to being applied onto the surface of the roof deck. The two parts include an isocyanate blend and a simple polyol blend. Upon mixing, the isocyanate blend reacts or crosslinks with the simple polyol blend to form the polyurethane adhesive.
However, these conventional two-part polyurethane adhesives are sensitive to weather conditions due to the effects of temperature on the viscosity, and therefore the reaction speed, of the adhesive. Accordingly, conventional two-part polyurethane adhesives are packaged and formulated into various grades, such as Summer, Winter, and Regular, that vary the composition of the adhesive in order to account for temperature.
One solution to the problem of temperature effects on conventional two-part polyurethane adhesives is to use a high-viscosity adhesive. However, the applicator systems used to apply the adhesives to the roofing substrate are pump driven and oftentimes are unable to reliably pump high-viscosity two-part polyurethane adhesives. Therefore, there is room in the art for a pump driven applicator system that reliably pumps high viscosity adhesives.